186,953 research outputs found
A New Macroeconomic Time Series: Business Profitability in Twentieth-Century Australia
Get PDFMacroeconomic time series, business profitability, Australia
Water quality monitoring, control and management (WQMCM) framework using collaborative wireless sensor networks
No full textImproving water quality is of global concern, with agricultural practices being the major contributors to reduced water quality. The reuse of nutrient-rich drainage water can be a valuable strategy to gain economic-environmental benefits. However, currently the tools and techniques to allow this do not exist. Therefore, we have proposed a framework, WQMCM, which utilises increasingly common local farm-scale networks across a catchment, adding provision for collaborative information sharing. Using this framework, individual sub-networks can learn their environment and predict the impact of catchment events on their locality, allowing dynamic decision making for local irrigation strategies. Since resource constraints of network nodes (e.g. power consumption, computing power etc.) require a simplified predictive model for discharges, therefore low-dimensional model parameters are derived from the existing National Resource Conservation Method (NRCS), utilising real-time field values. Evaluation of the predictive models, developed using M5 decision trees, demonstrates accuracy of 84-94% compared with the traditional NRCS curve number model. The discharge volume and response time model was tested to perform with 6% relative root mean square error (RRMSE), even for a small training set of around 100 samples; however the discharge response time model required a minimum of 300 training samples to show reasonable performance with 16% RRMS
Agroeca dentigera Kulczynski, 1913, a liocranid spider new to Britain (Araneae, Liocranidae)
No full textFelton, C. J., Merrett, P. (2004): Agroeca dentigera Kulczynski, 1913, a liocranid spider new to Britain (Araneae, Liocranidae). Bulletin of the British Arachnological Society 13 (1): 90-92, DOI: 10.5281/zenodo.81980
Empirical Evaluation of OI-MAC: Direct Interconnection between Wireless Sensor Networks for Collaborative Monitoring
No full textCooperation between co-located Wireless Sensor Networks (WSNs) has the potential to present new opportunities for novel applications and provide network performance improvements. The traditional interconnection approach for WSNs is based on a backbone network such as the Internet, but this may have intermittent or unavailable connectivity in remote locations. To address this, Opportunistic Direct Interconnection (ODI) has been proposed to allow distinct and independent WSNs to communicate directly with neighbouring networks, and OIMAC is a link-layer protocol which implements this functionality. However, OI-MAC has not been experimentally validated, instead with analysis performed through simulation. In this paper, we present a practical implementation of OI-MAC using two separate multi-hop networks with 6 sensor nodes in each. We validate its effective operation through experimentally obtained timing diagrams, sensor data output, and energy consumption. Results show successful cross-network packet communication, while networks remain independent by maintaining individual configurations and communication channels. Furthermore, we show that the process of discovering neighbouring networks has an insignificant impact on energy consumption
Tunable vibration energy harvester
Get PDFMachinery condition monitoring is an established application for wireless sensor networks and energy harvesting technologies. However, vibration energy harvesters are generally applicable only to fixed-frequency vibration sources, as commercial vibration energy harvesters are highly-tuned to specific frequencies. Attempts have been made to deliver a tunable vibration energy harvester, but up to now none have been applicable to real applications. This demonstrator is a tunable vibration-powered condition monitoring system which is applicable to internal combustion engines that run at variable speeds. It has been deployed and tested on a ferry's diesel engine
A hidden Markov model-based acoustic cicada detector for crowdsourced smartphone biodiversity monitoring
Get PDFIn recent years, the field of computational sustainability has striven to apply artificial intelligence techniques to solve ecological and environmental problems. In ecology, a key issue for the safeguarding of our planet is the monitoring of biodiversity. Automated acoustic recognition of species aims to provide a cost-effective method for biodiversity monitoring. This is particularly appealing for detecting endangered animals with a distinctive call, such as the New Forest cicada. To this end, we pursue a crowdsourcing approach, whereby the millions of visitors to the New Forest, where this insect was historically found, will help to monitor its presence by means of a smartphone app that can detect its mating call. Existing research in the field of acoustic insect detection has typically focused upon the classification of recordings collected from fixed field microphones. Such approaches segment a lengthy audio recording into individual segments of insect activity, which are independently classified using cepstral coefficients extracted from the recording as features. This paper reports on a contrasting approach, whereby we use crowdsourcing to collect recordings via a smartphone app, and present an immediate feedback to the users as to whether an insect has been found. Our classification approach does not remove silent parts of the recording via segmentation, but instead uses the temporal patterns throughout each recording to classify the insects present. We show that our approach can successfully discriminate between the call of the New Forest cicada and similar insects found in the New Forest, and is robust to common types of environment noise. A large scale trial deployment of our smartphone app collected over 6000 reports of insect activity from over 1000 users. Despite the cicada not having been rediscovered in the New Forest, the effectiveness of this approach was confirmed for both the detection algorithm, which successfully identified the same cicada through the app in countries where the same species is still present, and of the crowdsourcing methodology, which collected a vast number of recordings and involved thousands of contributors.</p
Supercapacitor leakage in energy-harvesting sensor nodes: fact or fiction?
Get PDFAs interest in energy-harvesting sensor nodes continues to grow, the use of supercapacitors as energy stores or buffers is gaining popularity. The reasons for their use are numerous, and include their high power density, simple interfacing requirements, simpler measurement of state-of-charge, and a greater number of charging cycles than secondary batteries. However, supercapacitor energy densities are orders of magnitude lower. Furthermore, they have been reported to exhibit significant leakage, and this has been shown to increase exponentially with terminal voltage (and hence stored energy). This observation has resulted in a number of algorithms, designs and methods being proposed for effective operation of supercapacitor-based energy-harvesting sensor nodes. In this paper, it is argued that traditional ‘leakage’ is not as significant as has commonly been suggested. Instead, what is observed as leakage is in fact predominantly due to internal charge redistribution. As a result, it is suggested that different approaches are required in order to effectively utilize supercapacitors in energy-harvesting sensor nodes
Porrhomma cambridgei Merrett 1994
No full textPorrhomma cambridgei Merrett, 1994 Figs. 13A–F. Linyphia (?) oblonga O. Pickard-Cambridge, 1871 — O. Pickard-Cambridge (1871): p. 433 (descr. ♀); preoccupied, replaced by Merrett (1994). Microneta oblonga — Simon (1884): p. 441. Porrhomma oblongum — F. O. Pickard-Cambridge (1894): p. 102, Pl. II, Fig. 4 (♀, descr. ♂). considered a synonym of P. oblitum (O. Pickard-Cambridge, 1871) by Millidge & Locket (1952: p. 71). P. cambridgei Merrett, 1994 — Merrett (1994): p. 318, Figs. 1–4 (redescr. ♀); replacement name for P. oblongum; removed from synonymy of P. oblitum, contra Millidge & Locket (1952). Material examined. CZECHIA: Bohemian Karst, Srbsko, 2 May 1999, 1 ♀, 5 July 2000, 2 ♀, leg. et coll. L. Kubcová. Liteň, 7 Mar –12 Apr 2011, 2 ♀, leg. A. Tenčík. Vápenný Podol, Podolská and Páterova Caves, 22 May – 18 Nov 2003, 1 ♀; Moravian Karst, Harbešská Cave, 15 Aug 2008, 1 ♂ 1 ♀, leg. R. Mlejnek. Horka nad Moravou, 6 Mar–13 Nov 2008, 2 Ƌ 6 ♀, leg. V. Laška & I. H. Tuf. Jenišovice-Zalažany, Mravín, 18 Apr 2014 –29 Sep 2015, 5 ♂ 6 ♀; Pardubice-Polabiny, 28 Apr–23 Sep 2015, 1 ♀, leg. V. Růžička & J. Dolanský (IECA). Moravský Krumlov, Rokytná, 27 Apr 2002, 1 ♀, leg. V. Bryja (CVB). Diagnosis. Small species (CW <0.60 mm), Fe I–II without dorsal spines, AP has the form of a bird head, Sshaped ascending parts of copulatory ducts. It is closely similar to P. oblitum, but it can be distinguished by depigmented body and reduced eyes (Fig. 13A). Description. ♀ (from Horka nad Moravou, Czechia, 21 Aug–2 Oct 2008). Carapace pale yellow, 0.57 mm wide, eyes reduced, PME–PME = 2.3 (Fig. 13A). Abdomen pale. Fe without dorsal spines, Fe I with one prolateral spine. Ti I–II with one retrolateral spine. Tm Mt I = 0.39, Mt I/CW = 0.87. Ascending parts of the ducts are Sshaped. Spermathecae are formed behind the ascending part of the ducts (Figs. 13C–F). Ƌ (from Jenišovice-Zalažany, Mravín, Czechia, 18 Apr 2014 – 29 Sep 2015). Embolus of middle length with a narrow velum. AP has the form of a bird head (Fig. 13B). Variation. Ƌ ♀. Carapace 0.56–0.59 mm wide. Ti I sometimes with one prolateral spine. Tm Mt I = 0.39–0.41, Mt I/CW = 0.84–0.89 (n = 8) (Růžička et al. 2011; sub P. aff. myops). Comments. O. Pickard-Cambridge (1871) described that the species Linyphia (?) oblonga is characterised by “eyes very small”. Based on vulva structure, Millidge & Locket (1952) synonymised this microphthalmic form with Porrhomma oblitum. Finally, Merrett (1994) removed it from synonymy with P. oblitum and revalidated it as a separate species P. cambridgei. Genitalia are indistinguishable from those of P. oblitum. The species is clearly characterised by femora I and II without dorsal spines, cephalothorax width <0.58 mm and reduced eyes. I found no intermediate form between P. cambridgei and P. oblitum. Ecology. The species was collected on tree bark in the Bohemian Karst (Thaler et al. 2003), in detritus in this karst region, and in conglomerate terrains in southern Moravia. Other specimens were found in grasslands (Merrett 1994). However, the reduced eyes suggest that this species lives mainly in subterranean habitats. Růžička & Dolanský (2016) and Růžička et al. (2011, sub. P. aff. myops) documented the occurrence of this species in sandy marlite terrain, alluvial soils and in karst terrain (unpubl.) at a depth of 35–140 cm. Finally, P. cambridgei was collected in two karst caves at a depth of 60 m. Global distribution. Europe among southern England, northern Italy and the Czech Republic after Hänggi (1999), Zingerle (1999), Harvey et al. (2002), van Keer et al. (2016), Arachnologische Gesellschaft (2017), and this paper. See Fig. 14.Published as part of Růžička, Vlastimil, 2018, A review of the spider genus Porrhomma (Araneae, Linyphiidae), pp. 1-75 in Zootaxa 4481 (1) on pages 16-18, DOI: 10.11646/zootaxa.4481.1.1, http://zenodo.org/record/145473
Design of a linearized magnetic spring for body-worn inertial energy harvesters
Get PDFA potential method for powering body-worn sensors is that of inertial energy harvesting; extracting energy from the movement of the human body. However, the frequencies typically present are <5 Hz, hence requiring physically large devices. A promising solution utilizes a magnetic spring, but these exhibit a non-linear relationship between force (and hence resonant frequency) and displacement. This paper describes a design for implementing a linearized magnetic spring. Finite element analysis is used to model this device and compare against those reported in the literature. Simulation results indicate that, compared to the state-of-the-art, this design exhibits improved linearity (2%) across a wider displacement range (±25 mm). A prototype has been fabricated, and the simulation results experimentally validated
Automated negotiation for opportunistic energy trading between neighbouring wireless sensor networks
No full textAs the Internet of Things grows, the number of wireless sensor networks deployed in close proximity will continue to increase. By nature, these networks are limited by the battery supply that determines their lifetime and system utility. To counter such a shortcoming, energy harvesting technologies have become increasingly investigated to provide a perpetual energy source; however, new problems arise as a result of their wide spatio-temporal variation. In this paper, we propose opportunistic energy trading, which enables otherwise independent networks to be sustained by sharing resources. Our goal is to provide a novel cooperation model based on negotiation to solve coordination conflicts between energy harvesting wireless sensor networks. Results show that networks are able to satisfy their loads when they agree to cooperate
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